1. Field of the Invention
The present invention relates to an uninterruptible DC power system, (DC UPS) and more particularly, to an uninterruptible DC power system to be served as an emergency power source which is capable of effectively reducing the line loss when applied to electric appliances attached with AC/DC switchable power suppliers (SW power).
2. Description of the Prior Art
Utility electric power is relied on by common domestric consumers as their power source for electric appliances. In case of the occurrence of abnormal states such as power outage, an undervoltage, or a over voltage, or an abnormal frequency, the user""s loads loose their power supply so that the unterruptible power system (UPS) whose battery unit normally under floating charge state from the utility source takes over the responsibility for an emergency source to supply the emergency power to those user""s loads which have lost the utility power supply.
Normally, the power output of a conventional UPS is in the form of AC. The operational principle of an UPS is inputting the AC utility power by way of an AC to DC converter so as to store the DC energy in the UPS by a DC charging circuit, and then supplies the stored DC electric power to the loads by converting back to AC when the utility power is out thereby serving as a stand by power source. Meanwhile, in the aforesaid UPS scheme, the electric power is firstly converted from AC to DC, and then converted back from DC to AC, through repeated conversion of electric power as such, the electrical circuits used for such repeated conversion of power become complicated with increased circuit loss as well.
Therefore, an invention devoting to resolving aforesaid disadvantages of current UPS so as to upgrade the quality of the UPS is definitely necessary. The present inventor has delved into this matter with long time efforts and come to realization of the present invention.
It is a first object of the present invention to provide a newly developed DC UPS which is capable of reducing electric power loss during conversion so as to improve the efficiency and effectiveness of the system, and start a lighting equipment in case the utility AC voltage becomes abnormal.
It is a second object of the present invention to provide a newly developed DC UPS which is capable of maintaining a stable output voltage without being influenced by the input source.
It is a third object of the present invention to provide a newly developed DC UPS which is capable of performing power conversion by only one stage so as to minimized the complexity of the circuit scheme and also improve environmental conscious effect.
To achieve the aforesaid objects, the DC UPS of the present invention is composed of at least a AC voltage and frequency detecting circuit, an AC to DC conversion and charging circuit, a DC voltage conversion circuit, a load detecting circuit, an output voltage detecting circuit, and a control circuit. It is essentially emphasized that the invention is devoted to reducing the power loss owing to power conversion so as to improve the system efficiency and save energy. Moreover, the DC UPS of the present invention can maintain a stable output voltage, and by means of detecting utility AC voltage, a lighting equipment can be turned on to illuminate surroundings in case the utility supply voltage is found to be abnormal.